The present disclosure relates to a coil device, a method for manufacturing the coil device, and a wireless power transfer system-charger and a wireless power transfer system-device, which include the coil device.
In general, various electronic devices are equipped with batteries and operated using power charged in the batteries. In this case, the battery is replaceable and rechargeable in the electronic device. To this end, the electronic device is equipped with a connecting terminal for a connection with an external charging device. That is, the electronic device is electrically connected with the charging device through the connecting terminal. However, as the connecting terminal in the electronic device is exposed to the outside, the connecting terminal may be contaminated with foreign matters or short-circuited due to moisture. In this case, connection failures occur between the connecting terminal and the charging device, and therefore, the battery in the electronic device may not be charged.
In order to solve the above-described problem, there has been proposed a wireless power transfer (WPT) system for charging electronic devices by wireless.
The WPT system is a technology for transferring power by wireless through a space, and maximizes convenience of supplying power to mobile devices and digital home appliances.
The WPT system has advantages of power saving through real-time control of the use of power, the overcoming of space limitation of power supply, reduction in amount of waste batteries using battery recharging, and the like.
Representative examples of a scheme for implementing the WPT system are a magnetic induction scheme and a magnetic resonance scheme. The magnetic induction scheme is a non-contact energy transfer technology in which, when two coils approach each other, an electromotive force is generated in the other coil by the medium of magnetic flux generated as current flows in one coil, and a frequency of a few hundreds of kHz may be used in the magnetic induction scheme. The magnetic resonance scheme is a magnetic resonance technology using only electric or magnetic fields without using electromagnetic waves or current. In the magnetic resonance scheme, the distance at which power transfer is possible is a few meters or more, and hence a frequency of a few MHz may be used.
The WPT system includes a WPT system-charger for transferring power by wireless and a WPT system-device for receiving power to charge loads such as batteries. There has been developed a WPT system-charger which can select a charging scheme of a WPT system-device, i.e., any one of the magnetic induction scheme and the magnetic resonance scheme, and transfer power by wireless, corresponding to the charging scheme of the WPT system-device.
The PWT system may transfer power in such a manner that transfers, by wireless, an electromotive force induced on a coil.
As PWT systems become smaller in size, a space for disposing a coil is limited. In addition, when the coil becomes thin to increase the number of windings thereof, the resistance of the coil is increased, thereby lowering charging efficiency.